Mini Cylinders

[2airishuman]

Get one of these
Amazon.com : CO2 Inflator By PRO BIKE TOOL - Quick & Easy - Presta & Schrader Valve Compatible - Bicycle Tire Pump For Road & Mountain Bikes - Insulated Sleeve - No CO2 Cartridges Included : Sports & Outdoors

And a pack of these

Amazon.com : Crosman 12 Gram CO2 (40 Cartridges) : Hunting And Shooting Equipment : Sports & Outdoors

And for $40 you have 40 inflates.....

Those are 12g cartridges which each produce 6.5 liters of gas at the surface. That would give 6.5 kg or about 14 pounds of lift. Aquanomad mentions being unwilling to sacrifice "mix" so I presume these would be used at trimix depths. At, say, 130 feet, you'd get less than 3 pounds of lift per CO2 cartridge. A little searching shows that standard sizes for disposable prefilled CO2 cartridges go up to around 40g, with some odd manufacturer-specific sizes up to about twice that.

Spare air cylinders are available in 1.7 cf and 3.0 cf, which give 106 and 187 pounds of lift at the surface, respectively (in freshwater, a little more in the ocean), or around 25-50 pounds at 130 feet, probably in the ballpark.

Paintball cylinder sizes are quoted in cubic inches (ci) displacement. For comparison to (U.S.) scuba tank sizes, at 3000 PSI, 8.5 ci is equal to 1 cubic foot at surface pressure. Standard aluminum paintball cylinder sizes are 13, 35, 48, and 62 ci, which roughly correspond to 1.5, 4, 6, and 7 cubic feet. These are 3AL3000 DOT cylinders.

 

[2airishuman]

Some more on Spare Air. Here's a spec page, which confirms that the neck thread is 5/8" 18 UNF:

Submersible Systems, Inc. - Cylinders and Tanks

These are 3AL3000 cylinders. In addition to the common sizes (1.7 and 3.0), the spec page lists 1.1 and 2.7 cf. All are 2.25" in diameter and vary only in length.

If you look at paintball "remote lines" you'll see mating components for the paintball regulator output fitting, with a valve and NPT output that could be adapted to an SMB.

 

[Robert Creason]

This is an original copy of the Spare Air service manual, it was actually quite hard to find. Now, if only I can find a reasonable service parts kit supplier. Is there any dive shop owners that are also retailers of Spare Air that want to demonstrate free market capitalism and bend the rules a little to sell me a service parts kit?